1. Prior Art
The present invention relates to image data processing devices for generating graphic images using a plurality of processors for image data processing.
2. Description of the Prior Art
In case of parallel generating of graphic images using a multi-processor system, it is necessary for every processor to access to a frame buffer when each processor outputs calculated image data to a screen. Also, in the case of multi-window systems in which each window is processed by each previously assigned processor, it is required for every processor to access to the frame buffer as well as the multi-processor systems. The above type structure in which every processor shares one frame buffer causes access conflicts to the frame buffer, resulting in performance reduction.
A conventional image data processing system is such that a whole screen is divided into non-overlapping areas corresponding to the number of processors, and each processor is assigned to a frame buffer corresponding to each area, to resolve the access-conflict-problem.
However, the above mentioned conventional image data processing system lacks unlimited access ability for every processor, i.e., each processor's accessible area is limited to a specified one. This causes increasing of data communication volume between processors in running various types of application software, resulting in performance reduction.
For example, assume that a shaded image is generated by the Z-buffer method from a model formed by many polygons. Each processor is accessible to only a specified area of the frame buffer so that the processor is in charge of the specified area in image generating. However, it is not clear which area of the frame buffer each polygon occupies, so that each processor can't decide which polygon shape information should be fetched from a memory for itself. Therefore, every processor must refer to every polygon shape data. Supplying the shape data to every processor requires broadcast communication. However, the communication time is so constant not depending on the number of processors that increasing processors causes performance saturation because of tight communication time.